The present invention relates to an oxygen sensor arranged in the exhaust system of an internal combustion engine for a motor vehicle, for example, to sense the concentration of oxygen in exhaust gas.
Various oxygen sensors are available for general use. As disclosed in U.S. Pat. No. 6,477,887, an oxygen sensor comprises typically a sensor element for sensing an oxygen concentration and converting it to an electric signal, an element securing insulator having an element hole through which the sensor element is arranged, a sealing positioning portion for sealing a clearance between the element securing insulator and the sensor element by a glass sealant and positioning the sensor element in the element securing insulator, terminals arranged to be in press contact with respective contacts of the sensor element which protrude from the element securing insulator and for taking an output from the sensor element, a terminal holding insulator arranged on the top face of the element securing insulator and for holding the terminals, a holder arranged at the outer periphery of the element securing insulator and for holding the element securing insulator, a casing secured to the holder at a first end and for covering the outer periphery of the terminal holding insulator, and a protector secured to the holder at a second end and for covering the outer periphery of the sensor element protruding from the element securing insulator.
The oxygen sensor is secured to an exhaust pipe by engaging a thread of the holder with the exhaust pipe, and is disposed with its portion covered with the protector protruding into the exhaust pipe.